The invention relates to a method for demolding annular elastomeric molded parts from a mold core according to the preamble of claim 1 and to a device for carrying out such a method according to the preamble of claim 9.
The invention relates to a method for demolding annular elastomeric molded parts from a mold core according to the preamble of claim 1 and to a device for carrying out such a method according to the preamble of claim 9.
Nowadays, the production of elastomeric molded parts, in particular open rubber rings, takes place predominantly in an injection molding process, wherein a plurality of mold cavities in the form of half-shells arranged parallel on a mold core are molded. The counter-molds, as mold jaws fitted onto the mold core from the exterior, likewise contain mold cavities in the form of half-shells so that, with the mold jaws fitted on, annular mold cavities are produced into which rubber or plastic materials can be introduced which, after vulcanization, form annular molded parts. These are used in particular in waste water technology.
For demolding of the molded parts from the injection mold, first of all the outer mold jaws are removed from the mold core and then the molded parts, of which half of each one still remains in the mold cavities of the mold core, must be extracted from the mold core. Because of their elastomeric characteristics the molded parts are generally pulled in the longitudinal direction over the surface of the mold core and removed from the free end thereof.
From DE-OS 21 15 680 a stripping device is known which contains belts running in the axial direction of the mold core which are driven in opposite directions so that the stripping belts move to the free end of the mold core during the stripping operation and thus push the molded parts over the mold core.
DE 30 23 447 discloses a similar stripping device which is in each case designed as a rigid elongate body which can move in the stripping direction, set at an angle to the circumference of the rings to be stripped out, parallel to the axis of the mold core, and which can move back freely against the stripping direction. It is also known from this document that the stripping of the rings can be carried out alternatively by means of a compressed air device.
Finally, a similar device is known from DE 33 06 513, in which the stripper has a hook which engages behind the last ring in order to simplify the stripping.
Basically in all the aforementioned devices it is necessary that, for stripping, the rings have to be guided from the location where they are produced on the mold core, over the mold core to the free end of the mold core, wherein the mold cavities located along the extraction path are either still filled or are already empty. In any case the rings are pulled over a surface provided with troughs and peaks, which brings with it the great risk that the rings can be damaged or, in particular in the event of a greater diameter or a non-circular mold, become intertwined, so that after-treatment of the rings is necessary. A further disadvantage is that the illustrated stripping devices are difficult to set, since if the pressure on the molded parts is too low the devices are not capable of stripping out the molded parts over the entire displacement path, and if the pressure is too high the devices can cause damage to the rings. Furthermore, the mold cores are subjected to substantial wear, which is caused by abrasion of the stripper on the mold core.
Therefore, the object of the invention is to provide a method for demolding annular elastomeric molded parts from a mold core, wherein the molded parts can be extracted in a simple manner and very carefully from the mold core, wherein a rotation of the molded parts is avoided and the wear on a mold core is considerably reduced.
A further object of the invention is to provide a device for demolding annular elastomeric shaped parts that is constructed in a simple manner, avoids after-treatment of the molded parts and can be produced cost-effectively.
These objects are achieved by the invention set out in claims 1 and 9. Advantageous embodiments of the invention are set out in the subordinate claims.